DOCSLIB.ORG

Trends in the Stability of Antarctic Coastal Polynyas and the Role of Topographic Forcing Factors

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Trends in the Stability of Antarctic Coastal Polynyas and the Role of Topographic Forcing Factors remote sensing Article Trends in the Stability of Antarctic Coastal Polynyas and the Role of Topographic Forcing Factors Liyuan Jiang 1,2, Yong Ma 1, Fu Chen 1,*, Jianbo Liu 1, Wutao Yao 1,2 , Yubao Qiu 1 and Shuyan Zhang 1,2 1 Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China; [email protected] (L.J.); [email protected] (Y.M.); [email protected] (J.L.); [email protected] (W.Y.); [email protected] (Y.Q.); [email protected] (S.Z.) 2 School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China * Correspondence: [email protected]; Tel.: +86-010-8217-8158 Received: 2 February 2020; Accepted: 18 March 2020; Published: 24 March 2020 Abstract: Polynyas are an important factor in the Antarctic and Arctic climate, and their changes are related to the ecosystems in the polar regions. The phenomenon of polynyas is influenced by the combination of inherent persistence and dynamic factors. The dynamics of polynyas are greatly affected by temporal dynamical factors, and it is difficult to objectively reflect the internal characteristics of their formation. Separating the two factors effectively is necessary in order to explore their essence. The Special Sensor Microwave/Imager (SSM/I) passive microwave sensor has been making observations of Antarctica for more than 20 years, but it is difficult for existing current sea ice concentration (SIC) products to objectively reflect how the inherent persistence factors affect the formation of polynyas. In this paper, we proposed a long-term multiple spatial smoothing method to remove the influence of dynamic factors and obtain stable annual SIC products. A halo located on the border of areas of low and high ice concentration around the Antarctic coast, which has a strong similarity with the local seabed in outline, was found using the spatially smoothed SIC products and seabed. The relationship of the polynya location to the wind and topography is a long-understood relationship; here, we quantify that where there is an abrupt slope and wind transitions, new polynyas are best generated. A combination of image expansion and threshold segmentation was used to extract the extent of sea ice and coastal polynyas. The adjusted record of changes in the extent of coastal polynyas and sea ice in the Southern Ocean indicate that there is a negative correlation between them. Keywords: Southern Ocean; coastal polynyas; SIC; seabed 1. Introduction Polynyas are mesoscale phenomena that occur in the polar regions, and are important features of sea ice cover. The term refers to an area of open water in sea ice that remains ice free or covered by thin ice for a long time under weather conditions where sea water can freeze. Their horizontal scale ranges from 0.1 to 100 km, with areas in the range 10 to 105 km2 [1–9]. Polynyas are sensitive to climate change, and play an important role in air–sea interactions [6,9–11], halocline maintenance [3,11], and biodiversity [12–16]. The formation and expansion of a polynya is accompanied by salt precipitation during the freezing of sea water. The low temperature and high brine concentration produced in this process are an important source of dense polar water masses [17–19]. Polynyas play an important role in affecting the exchange of heat and moisture between the sea and the air [20–22]. The heat loss over thin ice (the polynya) can be several or even hundreds of times higher than the heat loss over thick ice Remote Sens. 2020, 12, 1043; doi:10.3390/rs12061043 www.mdpi.com/journal/remotesensing Remote Sens. 2020, 12, 1043 2 of 21 (the sea ice) [23,24]. The open waters of polynyas are also important habitats for birds and marine mammals [8,25,26]. Depending on which mechanism forms and maintains polynyas in high latitude oceans, polynyas can be divided into open-ocean and coastal polynyas [1,7,27,28]. The formation of open-ocean polynyas is mainly due to a vertical circulation pattern, known as a "sensible-heat polynya" [1,27,29]. Due to continuous convective mixing, the heat from the upwelling deep warm water rises to the surface layer, which prevents the formation of sea ice. The surface-cooled seawater then sinks to the bottom of the ocean and is replaced by more rising warm water [27]. Due to the complexity of the influencing factors, the mechanisms behind the formation and maintenance of open-ocean polynyas are still not fully understood. The essence of a coastal polynya, in contrast, is a region where ice is constantly generated near the shore and is continuously carried out into the ocean by the action of local winds or ocean currents, which balances the loss of heat to the atmosphere and maintains the amount of heat in the open water at the same time [3,5,8,27,29,30]. The heat released into the atmosphere from coastal polynyas is derived from the heat that is lost from seawater in the form of "latent heat" during freezing. Therefore, this type of polynya is also called a "latent-heat polynya" [1,27,30]. Coastal polynyas in Antarctica play an important role in the production of highly saline and highly dense water, which has a profound impact on the formation of the Antarctic bottom water [18,19,31,32]. There are many factors that influence the formation and persistence of polynyas. Very recent studies have suggested that landfast sea ice (fast ice) plays an important role in the formation and variability of the polynyas [33]. Surface winds over Antarctica are closely related to the orientation and surface ice topography [34]. The Ross Shelf polynya (RSP) was inhibited by large icebergs, and the new polynyas formed downwind of the icebergs [35]. Within the ocean circulation, terrain obstacles can enhance the upward flow of warm deep water, which is an important factor in the formation and maintenance of polynyas [27]. Gordon [36] proposed that the formation of the Weddell Polynya in the Southern Ocean is the result of vertical convective mixing of ocean currents and surface-warming seawater caused by the underwater Maud Rise near the polynya. Alverson [37] used numerical methods to study the formation of polynyas under the influence of topographical factors, and found that local convection above seamounts is enhanced, and that the surface buoyancy flux can drive the convection of deep water. Based on the time scale involved, these influencing factors can be categorized as dynamic factors or persistent ones. The dynamic factors refer to temporary dynamical factors affecting the formation and maintenance of polynyas over a short period of time, including short-term variations in climatic conditions that are disturbance factors, such as the wind, surface ocean currents, and surface salinity. These factors have a large effect on studies of the secular variation in a polynya. The persistent factors refer to intrinsic persistent factors that act on polynyas for a long time; these include ocean thermodynamic processes [38,39], topography, and ocean dynamic processes [27,40,41]. Under the combined effect of these various factors, polynyas change constantly. Thanks to the progress of remote sensing technology, it is now possible to use satellite sensors to monitor sea ice. However, coastal polynyas in the Southern Ocean are small-scale features that are difficult to monitor from satellite microwave radiometry. It is common to estimate the area of polynyas from SIC maps by using an ice concentration threshold. Passive microwave sensors are not restricted by the time of day, or influenced by clouds, and they have better space time continuity, which is important in the monitoring of sea ice in the polar regions. Markus and Burns proposed a polynya signature simulation method (PSSM) to estimate subpixel-scale coastal polynyas with satellite passive microwave data [42]. Several studies have generated polynyas detection and ice production estimation using polarization ratios from radiometer data [43,44]. A recent paper used a combination of the thermal infrared and passive microwave data to retrieve the sea ice production in polynyas [45]. At present, many kinds of SIC products are obtained from passive microwave remote sensing data [46,47], which provide sufficient data for monitoring polynyas. However, due to the influence of dynamic factors, some daily SIC products may show abrupt changes from one day to the next, and monthly products may vary greatly due to short-term climate anomalies in certain months. Additionally, the daily and Remote Sens. 2020, 12, 1043 3 of 21 monthly products can only provide information about polynyas over a short period of time, making it difficult to analyze the long-term stability of polynyas. What is more, current research on the factors affecting polynyas is limited to local areas and most studies are based on the results of simulation tests. The persistent factors are the decisive factors affecting the long-term stability of polynyas. Therefore, how to effectively remove the influence of dynamic factors and analyze the persistent factors affecting polynya formation and maintenance is an urgent problem that needs to be solved. In the present study, we proposed a spatial-temporal smoothing strategy to obtain SIC products covering a period of one year (365 days) from which the dynamic factors were removed by making use of the SIC monitoring product for many years. A combination of the buffer clip and threshold segmentation was used to extract the area of sea ice and coastal polynyas. This paper analyzed the correlation between the formation and persistence of coastal polynyas and the local topography in the Southern Ocean, as well as changes in the long-term stability of the polynyas, which is affected by persistent factors.
Load more

Recommended publications
  • Years at the Amery Ice Shelf in September 2019
    https://doi.org/10.5194/tc-2020-219 Preprint. Discussion started: 19 August 2020 c Author(s) 2020. CC BY 4.0 License. 1 Atmospheric extremes triggered the biggest calving event in more than 50 2 years at the Amery Ice shelf in September 2019 3 4 Diana Francis 1*, Kyle S. Mattingly 2, Stef Lhermitte 3, Marouane Temimi 1, Petra Heil 4 5 6 1 Khalifa University of Science and Technology, P. O. Box 54224, Abu Dhabi, United Arab 7 Emirates. 8 2 Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ, 9 USA. 10 3 Department of Geoscience and Remote Sensing, Delft University of Technology, Mekelweg 5, 11 2628 CD Delft, Netherlands. 12 4 University of Tasmania, Hobart, Tasmania 7001, Australia. 13 14 * Corresponding Author: [email protected]. 15 16 Abstract 17 Ice shelf instability is one of the main sources of uncertainty in Antarctica’s contribution to future 18 sea level rise. Calving events play crucial role in ice shelf weakening but remain unpredictable and 19 their governing processes are still poorly understood. In this study, we analyze the unexpected 20 September 2019 calving event from the Amery Ice Shelf, the largest since 1963 and which 21 occurred almost a decade earlier than expected, to better understand the role of the atmosphere in 22 calving. We find that atmospheric extremes provided a deterministic role in this event. The calving 23 was triggered by the occurrence of a series of anomalously-deep and stationary explosive twin 24 polar cyclones over the Cooperation and Davis Seas which generated strong offshore winds 25 leading to increased sea ice removal, fracture amplification along the pre-existing rift, and 26 ultimately calving of the massive iceberg.
    [Show full text]
  • Open-Ocean Polynyas and Deep Convection in the Southern Ocean Woo Geun Cheon1 & Arnold L
    www.nature.com/scientificreports OPEN Open-ocean polynyas and deep convection in the Southern Ocean Woo Geun Cheon1 & Arnold L. Gordon 2 An open-ocean polynya is a large ice-free area surrounded by sea ice. The Maud Rise Polynya in the Received: 27 December 2018 Southern Ocean occasionally occurs during the austral winter and spring seasons in the vicinity of Maud Accepted: 18 April 2019 Rise near the Greenwich Meridian. In the mid-1970s the Maud Rise Polynya served as a precursor to Published: xx xx xxxx the more persistent, larger Weddell Polynya associated with intensive open-ocean deep convection. However, the Maud Rise Polynya generally does not lead to a Weddell Polynya, as was the situation in the September to November of 2017 occurrence of a strong Maud Rise Polynya. Using diverse, long- term observation and reanalysis data, we found that a combination of weakly stratifed ocean near Maud Rise and a wind induced spin-up of the cyclonic Weddell Gyre played a crucial role in generating the 2017 Maud Rise Polynya. More specifcally, the enhanced fow over the southwestern fank of Maud Rise intensifed eddy activity, weakening and raising the pycnocline. However, in 2018 the formation of a Weddell Polynya was hindered by relatively low surface salinity associated with the positive Southern Annular Mode, in contrast to the 1970s’ condition of a prolonged, negative Southern Annular Mode that induced a saltier surface layer and weaker pycnocline. In the Southern Ocean there are two modes in which surface water can attain sufcient density to descend into the deep ocean1.
    [Show full text]
  • Antarctic Climate and Sea Ice Variability – a Brief Review Marilyn Raphael UCLA Geography
    Antarctic Climate and Sea Ice Variability – a Brief Review Marilyn Raphael UCLA Geography WRCP Workshop on Seasonal to Multi- Decadal Predictability of Polar Climate Mean annual precipitation produced by NCEP2 for the years 1979–99 (mm yr21water equivalent). Bromwich et al, 2004 A significant upward trend 11.3 to 11.7 mm yr22 for 1979–99 is found from retrieved and forecast Antarctic precipitation over the continent. (a) Monthly and (b) annual time series for the modeled precipitation over all of Antarctica. Bromwich et al, 2004 Spatial pattern of temperature trends (degrees Celsius per decade) from reconstruction using infrared (TIR) satellite data. a, Mean annual trends for 1957–2006; b, Mean annual trends for 1969–2000, c–f, Seasonal trends for 1957–2006: winter (June, July, August; c); spring (September, October, November; d); summer (December, January, February; e); autumn (March, April, May; f). Over the long term (150 years) Antarctica has been warming, recent cooling trends in the 1990s attributed to positive trend in the SAM offset this warming. (Schneider et al, 2006) – ice cores Warming of Antarctica extends beyond the Antarctic Peninsula includes most of west Antarctica. Except in autumn, warming is apparent across most of the continent but is significant only over west Antarctica including the Peninsula (Steig et al, 2009). 1957 – 2006 reconstruction from satellite data. Steig et al, 2009 Steig et al, 2009 – reconstruction based on satellite and station data annual warming of 0.18C per decade for 1957 – 2006; winter and spring leading. Chapman and Walsh, 2007 – reconstruction based on station data and oceanic records 1950-2002: warming across most of West Antarctica Monaghan et al, 2009 – reconstruction 190-2005: warming across West Antarctica in all seasons; significant in spring and summer Trends are strongly seasonal.
    [Show full text]
  • Weddell Sea Phytoplankton Blooms Modulated by Sea Ice Variability and Polynya Formation
    UC San Diego UC San Diego Previously Published Works Title Weddell Sea Phytoplankton Blooms Modulated by Sea Ice Variability and Polynya Formation Permalink https://escholarship.org/uc/item/7p92z0dm Journal GEOPHYSICAL RESEARCH LETTERS, 47(11) ISSN 0094-8276 Authors VonBerg, Lauren Prend, Channing J Campbell, Ethan C et al. Publication Date 2020-06-16 DOI 10.1029/2020GL087954 Peer reviewed eScholarship.org Powered by the California Digital Library University of California RESEARCH LETTER Weddell Sea Phytoplankton Blooms Modulated by Sea Ice 10.1029/2020GL087954 Variability and Polynya Formation Key Points: Lauren vonBerg1, Channing J. Prend2 , Ethan C. Campbell3 , Matthew R. Mazloff2 , • Autonomous float observations 2 2 are used to characterize the Lynne D. Talley , and Sarah T. Gille evolution and vertical structure of 1 2 phytoplankton blooms in the Department of Computer Science, Princeton University, Princeton, NJ, USA, Scripps Institution of Oceanography, Weddell Sea University of California, San Diego, La Jolla, CA, USA, 3School of Oceanography, University of Washington, Seattle, • Bloom duration and total carbon WA, USA export were enhanced by widespread early ice retreat and Maud Rise polynya formation in 2017 Abstract Seasonal sea ice retreat is known to stimulate Southern Ocean phytoplankton blooms, but • Early spring bloom initiation depth-resolved observations of their evolution are scarce. Autonomous float measurements collected from creates conditions for a 2015–2019 in the eastern Weddell Sea show that spring bloom initiation is closely linked to sea ice retreat distinguishable subsurface fall bloom associated with mixed-layer timing. The appearance and persistence of a rare open-ocean polynya over the Maud Rise seamount in deepening 2017 led to an early bloom and high annual net community production.
    [Show full text]
  • Development of a Pan‐Arctic Monitoring Plan for Polar Bears Background Paper
    CAFF Monitoring Series Report No. 1 January 2011 DEVELOPMENT OF A PAN‐ARCTIC MONITORING PLAN FOR POLAR BEARS BACKGROUND PAPER Dag Vongraven and Elizabeth Peacock ARCTIC COUNCIL DEVELOPMENT OF A PAN‐ARCTIC MONITORING PLAN FOR POLAR BEARS Acknowledgements BACKGROUND PAPER The Conservation of Arctic Flora and Fauna (CAFF) is a Working Group of the Arctic Council. Author Dag Vongraven Table of Contents CAFF Designated Agencies: Norwegian Polar Institute Foreword • Directorate for Nature Management, Trondheim, Norway Elizabeth Peacock • Environment Canada, Ottawa, Canada US Geological Survey, 1. Introduction Alaska Science Center • Faroese Museum of Natural History, Tórshavn, Faroe Islands (Kingdom of Denmark) 1 1.1 Project objectives 2 • Finnish Ministry of the Environment, Helsinki, Finland Editing and layout 1.2 Definition of monitoring 2 • Icelandic Institute of Natural History, Reykjavik, Iceland Tom Barry 1.3 Adaptive management/implementation 2 • The Ministry of Domestic Affairs, Nature and Environment, Greenland 2. Review of biology and natural history • Russian Federation Ministry of Natural Resources, Moscow, Russia 2.1 Reproductive and vital rates 3 2.2 Movement/migrations 4 • Swedish Environmental Protection Agency, Stockholm, Sweden 2.3 Diet 4 • United States Department of the Interior, Fish and Wildlife Service, Anchorage, Alaska 2.4 Diseases, parasites and pathogens 4 CAFF Permanent Participant Organizations: 3. Polar bear subpopulations • Aleut International Association (AIA) 3.1 Distribution 5 • Arctic Athabaskan Council (AAC) 3.2 Subpopulations/management units 5 • Gwich’in Council International (GCI) 3.3 Presently delineated populations 5 3.3.1 Arctic Basin (AB) 5 • Inuit Circumpolar Conference (ICC) – Greenland, Alaska and Canada 3.3.2 Baffin Bay (BB) 6 • Russian Indigenous Peoples of the North (RAIPON) 3.3.3 Barents Sea (BS) 7 3.3.4 Chukchi Sea (CS) 7 • Saami Council 3.3.5 Davis Strait (DS) 8 This publication should be cited as: 3.3.6 East Greenland (EG) 8 Vongraven, D and Peacock, E.
    [Show full text]
  • Glacial Ocean Circulation and Stratification Explained by Reduced
    Glacial ocean circulation and stratification explained by reduced atmospheric temperature Malte F. Jansena,1 aDepartment of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637 Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved November 7, 2016 (received for review June 27, 2016) Earth’s climate has undergone dramatic shifts between glacial and We test the connection between atmospheric temperature interglacial time periods, with high-latitude temperature changes and ocean circulation and stratification changes, using idealized on the order of 5–10 ◦C. These climatic shifts have been asso- numerical simulations, which allow us to isolate the proposed ciated with major rearrangements in the deep ocean circulation mechanism. We use a coupled ocean–sea-ice model, with atmo- and stratification, which have likely played an important role in spheric temperature, winds, and evaporation–precipitation pre- the observed atmospheric carbon dioxide swings by affecting the scribed as boundary conditions (Materials and Methods). The partitioning of carbon between the atmosphere and the ocean. model uses an idealized continental configuration resembling the The mechanisms by which the deep ocean circulation changed, Atlantic and Southern Oceans, where the most elemental circu- however, are still unclear and represent a major challenge to our lation changes have been inferred (3, 5, 6, 12). understanding of glacial climates. This study shows that vari- ous inferred changes in the deep ocean circulation and stratifica- Results tion between glacial and interglacial climates can be interpreted We first focus on the model’s ability to reproduce key features as a direct consequence of atmospheric temperature differences.
    [Show full text]
  • Ice Production in Ross Ice Shelf Polynyas During 2017–2018 from Sentinel–1 SAR Images
    remote sensing Article Ice Production in Ross Ice Shelf Polynyas during 2017–2018 from Sentinel–1 SAR Images Liyun Dai 1,2, Hongjie Xie 2,3,* , Stephen F. Ackley 2,3 and Alberto M. Mestas-Nuñez 2,3 1 Key Laboratory of Remote Sensing of Gansu Province, Heihe Remote Sensing Experimental Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China; [email protected] 2 Laboratory for Remote Sensing and Geoinformatics, Department of Geological Sciences, University of Texas at San Antonio, San Antonio, TX 78249, USA; [email protected] (S.F.A.); [email protected] (A.M.M.-N.) 3 Center for Advanced Measurements in Extreme Environments, University of Texas at San Antonio, San Antonio, TX 78249, USA * Correspondence: [email protected]; Tel.: +1-210-4585445 Received: 21 April 2020; Accepted: 5 May 2020; Published: 7 May 2020 Abstract: High sea ice production (SIP) generates high-salinity water, thus, influencing the global thermohaline circulation. Estimation from passive microwave data and heat flux models have indicated that the Ross Ice Shelf polynya (RISP) may be the highest SIP region in the Southern Oceans. However, the coarse spatial resolution of passive microwave data limited the accuracy of these estimates. The Sentinel-1 Synthetic Aperture Radar dataset with high spatial and temporal resolution provides an unprecedented opportunity to more accurately distinguish both polynya area/extent and occurrence. In this study, the SIPs of RISP and McMurdo Sound polynya (MSP) from 1 March–30 November 2017 and 2018 are calculated based on Sentinel-1 SAR data (for area/extent) and AMSR2 data (for ice thickness).
    [Show full text]
  • Antarctic Sea Ice Control on Ocean Circulation in Present and Glacial Climates
    Antarctic sea ice control on ocean circulation in present and glacial climates Raffaele Ferraria,1, Malte F. Jansenb, Jess F. Adkinsc, Andrea Burkec, Andrew L. Stewartc, and Andrew F. Thompsonc aDepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; bAtmospheric and Oceanic Sciences Program, Geophysical Fluid Dynamics Laboratory, Princeton, NJ 08544; and cDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 Edited* by Edward A. Boyle, Massachusetts Institute of Technology, Cambridge, MA, and approved April 16, 2014 (received for review December 31, 2013) In the modern climate, the ocean below 2 km is mainly filled by waters possibly associated with an equatorward shift of the Southern sinking into the abyss around Antarctica and in the North Atlantic. Hemisphere westerlies (11–13), (ii) an increase in abyssal stratifi- Paleoproxies indicate that waters of North Atlantic origin were instead cation acting as a lid to deep carbon (14), (iii)anexpansionofseaice absent below 2 km at the Last Glacial Maximum, resulting in an that reduced the CO2 outgassing over the Southern Ocean (15), and expansion of the volume occupied by Antarctic origin waters. In this (iv) a reduction in the mixing between waters of Antarctic and Arctic study we show that this rearrangement of deep water masses is origin, which is a major leak of abyssal carbon in the modern climate dynamically linked to the expansion of summer sea ice around (16). Current understanding is that some combination of all of these Antarctica. A simple theory further suggests that these deep waters feedbacks, together with a reorganization of the biological and only came to the surface under sea ice, which insulated them from carbonate pumps, is required to explain the observed glacial drop in atmospheric forcing, and were weakly mixed with overlying waters, atmospheric CO2 (17).
    [Show full text]
  • Chapter 7 Arctic Oceanography; the Path of North Atlantic Deep Water
    Chapter 7 Arctic oceanography; the path of North Atlantic Deep Water The importance of the Southern Ocean for the formation of the water masses of the world ocean poses the question whether similar conditions are found in the Arctic. We therefore postpone the discussion of the temperate and tropical oceans again and have a look at the oceanography of the Arctic Seas. It does not take much to realize that the impact of the Arctic region on the circulation and water masses of the World Ocean differs substantially from that of the Southern Ocean. The major reason is found in the topography. The Arctic Seas belong to a class of ocean basins known as mediterranean seas (Dietrich et al., 1980). A mediterranean sea is defined as a part of the world ocean which has only limited communication with the major ocean basins (these being the Pacific, Atlantic, and Indian Oceans) and where the circulation is dominated by thermohaline forcing. What this means is that, in contrast to the dynamics of the major ocean basins where most currents are driven by the wind and modified by thermohaline effects, currents in mediterranean seas are driven by temperature and salinity differences (the salinity effect usually dominates) and modified by wind action. The reason for the dominance of thermohaline forcing is the topography: Mediterranean Seas are separated from the major ocean basins by sills, which limit the exchange of deeper waters. Fig. 7.1. Schematic illustration of the circulation in mediterranean seas; (a) with negative precipitation - evaporation balance, (b) with positive precipitation - evaporation balance.
    [Show full text]
  • Tidal Modulation of Antarctic Ice Shelf Melting Ole Richter1,2, David E
    Tidal Modulation of Antarctic Ice Shelf Melting Ole Richter1,2, David E. Gwyther1, Matt A. King2, and Benjamin K. Galton-Fenzi3 1Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, TAS, 7001, Australia. 2Geography & Spatial Sciences, School of Technology, Environments and Design, University of Tasmania, Hobart, TAS, 7001, Australia. 3Australian Antarctic Division, Kingston, TAS, 7050, Australia. Correspondence: Ole Richter ([email protected]) This is a non-peer reviewed preprint submitted to EarthArXiv. This preprint has also been submitted to The Cryosphere for peer review. 1 Abstract. Tides influence basal melting of individual Antarctic ice shelves, but their net impact on Antarctic-wide ice-ocean interaction has yet to be constrained. Here we quantify the impact of tides on ice shelf melting and the continental shelf seas 5 by means of a 4 km resolution circum-Antarctic ocean model. Activating tides in the model increases the total basal mass loss by 57 Gt/yr (4 %), while decreasing continental shelf temperatures by 0.04 ◦C, indicating a slightly more efficient conversion of ocean heat into ice shelf melting. Regional variations can be larger, with melt rate modulations exceeding 500 % and temperatures changing by more than 0.5 ◦C, highlighting the importance of capturing tides for robust modelling of glacier systems and coastal oceans. Tide-induced changes around the Antarctic Peninsula have a dipolar distribution with decreased 10 ocean temperatures and reduced melting towards the Bellingshausen Sea and warming along the continental shelf break on the Weddell Sea side. This warming extends under the Ronne Ice Shelf, which also features one of the highest increases in area-averaged basal melting (150 %) when tides are included.
    [Show full text]
  • POLYNYAS in the CANADIAN ARCTIC Analysis of MODIS Sea Ice Temperature Data Between June 2002 and July 2013
    Canatec Associates International Ltd. POLYNYAS IN THE CANADIAN ARCTIC Analysis of MODIS Sea Ice Temperature Data Between June 2002 and July 2013 David Currie 7/16/2014 Using daily sea ice temperature grids produced from MODIS optical satellite imagery, polynya occurrences in the Canadian Arctic and Northwest Greenland were mapped with a spatial resolution of one square kilometer and a temporal resolution of one week. The eleven year dataset was used to identify and measure locations with a high probability of open water occurrence. This approach appears to be most suitable for the spring months, when polynyas and shore leads represent the only open water in the region. An analysis of the results at several geographic scales reveals considerable yearly variation in polynya extents, although the relatively short period studied makes identifying trends rather difficult. Contents Introduction ................................................................................................................................................................ 3 Goals ............................................................................................................................................................................... 5 Source Data ................................................................................................................................................................. 6 MODIS Sea Ice Temperature Product MOD29/MYD29 ....................................................................... 6 Landsat Quicklook
    [Show full text]
  • Mid-Holocene Antarctic Sea-Ice Increase Driven by Marine Ice Sheet Retreat
    https://doi.org/10.5194/cp-2020-3 Preprint. Discussion started: 26 February 2020 c Author(s) 2020. CC BY 4.0 License. 1 FRONT MATTER 2 Title 3 Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat 4 Authors 5 Kate E. Ashley1*, James A. Bendle1, Robert McKay2, Johan Etourneau3, Francis J. Jimenez-Espejo3,4, 6 Alan Condron5, Anna Albot2, Xavier Crosta6, Christina Riesselman7,8, Osamu Seki9, Guillaume Massé10, 7 Nicholas R. Golledge2,11, Edward Gasson12, Daniel P. Lowry2, Nicholas E. Barrand1, Katelyn Johnson2, 8 Nancy Bertler2, Carlota Escutia3 and Robert Dunbar13. 9 Affiliations 10 1School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, 11 Birmingham, B15 2TT, UK 12 2Antarctic Research Centre, Victoria University of Wellington, Wellington 6140, New Zealand 13 3Instituto Andaluz de Ciencias de la Tierra (CSIC), Avenida de las Palmeras 4, 18100 Armilla, Granada, 14 Spain 15 4Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology 16 (JAMSTEC), Yokosuka 237-0061, Japan 17 5Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 18 02543, USA 19 6UMR-CNRS 5805 EPOC, Université de Bordeaux, 33615 Pessac, France 20 7Department of Geology, University of Otago, Dunedin 9016, New Zealand 21 8Department of Marine Science, University of Otago, Dunedin 9016, New Zealand 22 9Institite of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido, Japan 23 10TAKUVIK, UMI 3376 UL/CNRS, Université Laval, 1045 avenue de la Médecine, Quebec City, 24 Quebec, Canada G1V 0A6 25 11GNS Science, Avalon, Lower Hutt 5011, New Zealand 26 12Department of Geography, University of Sheffield, Winter Street, Sheffield, S10 2TN, UK 27 13Department of Environmental Earth Systems Science, Stanford University, Stanford, A 94305-2115 28 29 *Corresponding Author: email: [email protected] Climate of The Past Ashley et al., 2019 Submitted Manuscript Page 1 of 36 https://doi.org/10.5194/cp-2020-3 Preprint.
    [Show full text]